In the control of internal combustion engines, the conventional practice utilizes electronic control units, volatile and non-volatile memory, input and output driver circuitry, and a processor capable of executing a stored instruction set, to control the various functions of the engine and its associated systems. A particular electronic control unit communicates with numerous sensors, actuators, and other control units necessary to effect various control and information functions of the engine and/or vehicle.
Various sensors are used to detect engine operating parameters which may affect control of the engine and/or vehicle. However, many engine operating parameters or conditions are not directly measured or sensed due to the associated cost and/or availability of suitable sensors relative to the perceivable improvement in engine control. These parameters or conditions may be sensed or measured indirectly by sensing a related process or parameter using other sensors, or may be calculated or inferred. For example, torque sensors, while available, are not often used in vehicular applications. Likewise, it may be desirable to determine peak combustion temperature or pressure to improve the efficiency and reduce emissions related to the combustion process. As is known, lower than optimal combustion temperatures may result in white smoke while higher combustion temperatures result in increased production of oxides of nitrogen, and may result in engine damage if excessive. However, the harsh environment present within the cylinders is generally not amenable to temperature and/or pressure sensors for production use.
Temperature sensors are commonly used to detect the temperature of various engine and/or vehicle fluids (including air) to control associated engine components, including valves, heaters, shutters, and various other mechanisms. As is known, ambient and operating temperature variations may present a number of challenges in controlling the engine. Temperature-related complications may include fuel coagulation, insufficient coolant circulation, and increased exhaust emissions, among others. Conventional engine systems use the engine coolant temperature or engine oil temperature to activate various engine mechanisms in an effort to improve engine performance. However, a single fluid temperature measurement is not necessarily indicative of the current engine operating conditions which may be used to control one or more engine and/or vehicle devices. As such, it would be desirable to provide a system and method for detecting a cold engine based on signals from a plurality of engine temperature sensors.